如何在 Silverlight 的自定义控件中订阅 Attached 属性的事件？

Question

我正在开发可用于在我的应用 UI 中进行交互的自定义​​控件。所以，我的想法是控件将绑定到IInteractionsProvider，它有它的事件。然后，我将调用此提供程序上的方法，该方法将向我的控件引发事件以执行它需要执行的操作。

问题是，我不知道如何在我的自定义控件中正确订阅事件InteractionRequired。

基本上，我不知道如何正确地挂钩和取消挂钩事件以及在什么时间在控制范围内。

public interface IInteractionsProvider
    {
        event EventHandler InteractionRequested;

        void RequestInteraction(Action<object> callback);
    } 



public class MyInteractions : Control
    {
        public static readonly DependencyProperty ContainerProperty =
            DependencyProperty.Register("Container", typeof(Grid), typeof(IdattInteractions), new PropertyMetadata(null));

        public static readonly DependencyProperty InteractionsProviderProperty =
            DependencyProperty.Register("InteractionsProvider", typeof(IInteractionsProvider), typeof(IdattInteractions), new PropertyMetadata(null));

        public IdattInteractions()
        {
            DefaultStyleKey = typeof(MyInteractions);
        }

        public Grid Container
        {
            get { return GetValue(ContainerProperty) as Grid; }
            set { this.SetValue(ContainerProperty, value); }
        }

        public IInteractionsProvider InteractionsProvider
        {
            get { return (IInteractionsProvider)GetValue(InteractionsProviderProperty); }
            set { this.SetValue(InteractionsProviderProperty, value); }
        }

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            if (System.ComponentModel.DesignerProperties.IsInDesignTool) return;

            if (this.InteractionsProvider == null)
            {
                throw new NotSupportedException("InteractionsProvider wasn't specified. If you don't need interactions on this view - please remove MyInteractions from XAML");
            }

            if (this.Container != null)
            {
                if (this.Container.GetType() != typeof(Grid))
                {
                    throw new NotSupportedException("Specified container must be of Grid type");
                }
            }
            else
            {
                this.Container = TreeHelper.FindParentGridByName(this, "LayoutRoot") ?? TreeHelper.FindParent<Grid>(this);

                if (this.Container == null)
                {
                    throw new NotSupportedException("Container wasn't specified and parent Grid wasn't found");
                }
            }
        }
    }

Answer 1

这是你要找的吗？

public IInteractionsProvider InteractionsProvider 
{ 
    get { return (IInteractionsProvider)GetValue(InteractionsProviderProperty); } 
    set {
        var oldValue = this.InteractionsProvider;
        if (oldValue != null)
            oldValue.InteractionRequested -= this.HandleInteractionRequested;
        if (value != null)
            value.InteractionRequested += this.HandleInteractionRequested;
        this.SetValue(InteractionsProviderProperty, value);
    } 
} 

private void HandleInteractionRequested(object sender, EventArgs e)
{
    //...
}

Answer 2

要附加到依赖属性上的事件（或在分配后对依赖属性执行任何操作），您可以使用PropertyMetadata 上的回调委托。

    public static readonly DependencyProperty InteractionsProviderProperty = 
        DependencyProperty.Register("InteractionsProvider", typeof(IInteractionsProvider), typeof(IdattInteractions), new PropertyMetadata(null, OnInteractionsProviderPropertyChanged)); 

    private static void OnInteractionsProviderPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {

         var source = d As MyInteractions;
         if (source ! = null)
         {
             var oldValue = (IInteractionsProvider)e.OldValue;
             var newValue = (IInteractionsProvider)e.NewValue;
             source.OnInteractionsProviderPropertyChanged(oldValue, newValue);
         }
    }
    private void OnInteractionsProviderPropertyChanged(IInteractionsProvider oldValue, IInteractionsProvider newValue)
    {
         if (oldValue != null)
              oldValue -= InteractionsProvider_InteractionRequested;

         if (newValue != null)
              newValue += InteractionsProvider_InteractionRequested;
    }
    private void InteractionsProvider_InteractionRequested(object sender, EventArgs e)
    {
        // Do Stuff
    }